Production of titanium trihalides



Unimd States Patent C PRODUCTION or TITANIUM TRIHALIDES Anthony J. Kolk,In, South Euclid, and Dwight E. Davis, Hudson, Ohio, assignors, by mesneassignments, to Horizons Titanium Incorporated, Princeton, N.J., acorporation of New Jersey No Drawing. Application February 13, 1956Serial No. 564,880

5 Claims. (Cl. 204-64) This invention relates to the preparation ofcompounds of titanium in which the titanium is trivalent. Moreparticularly, it relates to the preparation of titanium trifluoride ortitanium trichloride in the form of a product admirably suited to beelectrolytically decomposed to yield titanium metal.

Trivalent titanium compounds are assuming increasing importance as rawmaterials from which titanium metal can be produced. Recently disclosedprocesses include, among others, the electrolysis of a fused salt bathcomposed of one or more alkali or alkaline earth metal halides andcontaining a halide of titanium in which the titanium has a valence ofless than four, for example, three or even two.

When a hydrogen halide is passed over titanium carbide at a temperaturebetween about 250 C. and 500 C., we have observed that a titanium'tn'halide forms on the surface of the titanium carbide, but thereaction ceases after a very short interval of time, probably bccausethe trihalide is deposited as a solid, coating the carbide andpreventing it from taking part in further reaction.

In accordance with the procedures developed by us, we have found thatthe titanium carbide may be completely reacted with the hydrogen halideto produce the desired trihalide without the cessation of the reactionpreviously noted, by suitably controlling the conditions under whichtitanium carbide and certain hydrogen halides are brought together, werecover a composition containing chlorine or fluorine compounds of thetitanium in trivalent form and containing one or more halide compoundsof the alkali or alkaline earth metals.

Titanium carbide, hydrogen chloride, hydrogen fluoride and the alkalimetal and alkaline earth metal halides are all available commercially ofsuflicient purity for effecting the desired reaction. It is preferablethat the carbide be in finely divided form, e.g. minus 100 mesh (TylerStandard), or finer. The carbide may, if desired, be readily preparedfrom titanium dioxide and carbon, in a manner well known in the art. Byemploying a pigment grade titanium dioxide and pure carbon, a product isobtained substantially free from contamination, except possibly, forsmall amounts of free carbon.

In our process, finely divided titanium carbide and a material in whichthe lower valent halide formed will dissolve are disposed in a suitableinert container, such as a porcelain boat in a hot tube furnace or agraphite crucible provided with means to heat the contents thereof; thecontents are heated to melt the alkali metal halide or alkaline earthmetal halide and then a flow of HCl or HF, to which TiCL; or TiF haspreferably been added in a small amount to the HCl or HF, is initiatedthrough the tube or into the furnace, while maintaining the temperatureof the charge well above that necessary to melt the alkali metal halideor alkaline earth metal halide.

The following reactions proceed with increasing intensity:

where X represents one or more alkali metals or alkaline earth metals.Up to temperatures of about 600 C., the reaction has been found toproceed at a satisfactory rate. At temperatures above 800 C., thetetrahalide is formed almost exclusively.

As indicated in the above equations, the presence of some tetrahalide isadvantageous in suppressing the formation of additional tetrahalide.Care must, however, be taken to avoid adding amounts of the tetrahalidein excess of that which would remain in equilibrium under the reactionconditions, since any excess would tend to react directly with thecarbide until the concentration fell to an equilibrium value. The smallamount of tetrahalide circulates and is recovered separately andrecycled through the system. The hydrogen may be employed toreconstitute additional hydrogen halide, e.g., by burning with chlorineor fluorine, and the carbon may be used to form additional titaniumcarbide.

Because the reactions are carried out in an environment in which thelower valent halide dissolves, for instance, in a fused salt meltcomprised of at least one alkali metal halide or alkaline earth metalhalide, the trivalent halide product does not coat the titanium carbideand form a barrier preventing the reaction from proceeding to thecomplete conversion of the titanium carbide. Preferably the halogencomponent of the fused melt is the same as that of the hydrogen halide.The fused melt should be oxygen-free and anhydrous and this may beachieved by drying the alkali or alkaline earth metal halide in acurrent of air heated to about170 C. or by drying the salts attemperatures of about C. under a vacuum.

In the above reactions, the alkali or alkaline earths in the charge formfused baths which are preferably eutectic compositions of two or morealkali or alkaline earth metal chlorides or fluorides, selected so as toprovide a stable bath which is molten at temperatures upwards of 350 C.Compositions with suitable melting temperatures may be readily found inthe literature. The solid titanium carbide is introduced into the bathas a finely divided particulate material. Once the bath is molten,hydrogen chloride or hydrogen fluoride is introduced into the meltthrough a suitable inlet tube of graphite or ceramic, provided with astrainer-like plate on the extremity which is immersed in the melt inorder to cause the hydrogen halide to be dispersed as it enters themelt. A reaction between the titanium carbide and the HCl or HP promptlyensues with the resultant formation of TiCl or TiF Because thetrihalides are soluble or form complexes in the fused melt, they arereadily taken upin the melt instead of coating the particles of carbideand hence, the carbide particles continuously present a fresh surface,constantly ready to participate in the desired reaction.

The following examples will further serve to illustrate the featurescharacterizing our invention:

Example I A mixture of 45 parts by weight of dry reagent grade LiCl, 55parts by weight of dry reagent grade KCl, and 50 parts by weight of TiCwas prepared. The mixture of dry ingredients was placed in a graphitecrucible which was then placed in a furnace provided with means foradmitting gaseous reactants and for discharging the reaction products,as well as with means for maintaining an inert atmosphere therein. Thefurnace was flushed 3 with dry argon and'the argon atmosphere wasmaintained throughout the preparation. The mixture was heated untilmolten and the temperature was thereafter maintained at 450 C. A streamof dry hydrogen chloride was bubbled into the molten mixture through asparging tube. Some fuming, indicating TiCl formation was noted. Afterfour hours, the reaction was discontinued by terminating the flow ofHCl. The salt melt had a faint yellowish green color, characteristic oflower valent titanium. The trivalent titanium amounted to 3% by weightof the melt. The melt containing titanium trichloride produced in thisfashion was used to produce metal by electrolysis of the fused melt, bytechniques known in the art.

Example I] A mixture was prepared from 500 parts by weight of reagentgrade sodium chloride and 100 parts by Weight of titanium carbide. Themixture was placed in a graphite crucible which was placed in a furnace.The furnace was flushed with a dry inert gas, argon, and the argonatmosphere was maintained throughout the preparation. The materials wereheated to just above the melting point of sodium chloride. A stream ofdry hydrogen chloride was then bubbled into the molten mixture through asparging tube. The hydrogen chloride sweep was maintained for 3 hours,when the desired concentration of titanium trichloride had beenobtained. At the temperature of operation, that is, about 800 C., muchof the titanium content is evolved as TiCl Under these conditions ofoperation about 1.52.0% titanium trichloride was retained in the fusedsalt. The resultant product was found to be suitable for electrolysis torecover titanium metal as a cathode deposit.

Example III Example I was repeated, using the corresponding fluorideinstead of the chlorides. The temperature of operation was. 700 C.Substantially the same results are noted.

We claim:

1. A process for preparing a fused salt composition containing atrihalide of titanium from the group consisting of titanium trichlorideand titanium tn'fiuoride and adapted to be electrolyzed to producetitanium metal which comprises: forming an anhydrous melt consisting ofat least one halide salt from the group consisting of alkali metalhalides and alkaline earth metal halides and which is stable attemperatures above 350 (3.; charging particles of finely dividedtitanium carbide into said melt while it is maintained molten at atemperature below about 600 (3.; and introducing a halide from the groupconsisting of HF and HCl into said carbide-containing melt wherein itreacts with the carbide to form the corresponding titanium trihalide insaid melt.

2. The process of claim 1 in which an inert atmosphere is maintainedover the melt during the process.

3. The process of claim 1 in which the fused salt product containing thetitanium trihalide is subsequently electrolyzed to produce titaniummetal.

4. The process of claim 1 in which a minor amount of a titaniumtetrahalide from the group consisting of TlCl4 and TiF is added to thehydrogen halide being introduced into said melt.

5. A process for preparing a fused salt composition containing titaniumtrichloride and adapted to be electrolyzed to produce titanium metalwhich comprises: forming an anhydrous melt consisting of at least onealkali metal chloride and which is stable at temperatures above 350 C.;maintaining an inert atmosphere over said melt; charging particles offinely divided titanium carbide into said melt while it is maintainedmolten at a temperature below about 600 C.; and introducing hydrogenchloride into said carbide-containing melt wherein it reacts with thecarbide to form titanium trichloride in the melt.

References Cited in the file of this patent UNITED STATES PATENTS1,845,342 Saklatwalla Feb. 16, 1932 2,184,884 Muskat et al Dec. 26, 19392,783,142 Singleton et a1 Feb. 26, 1957 FOREIGN PATENTS 141,908 GreatBritain Apr. 29, 1920 164,283 Australia Apr. 8, 1954

1. A PROCESS FOR PREPARING A FUSED SALT COMPOSITION CONTAINING ATRIHALIDE OF TITANIUM FROM THE GROUP CONSISTING OF TITANIUM TRICHLORIDEAND TITANIUM TRIFLUORIDE AND ADAPTED TO BE ELECTROLYZED TO PRODUCETITANIUM METAL WHICH COMPRISES: FORMING AN ANHYDROUS MELT CONSISTING OFAT LEAST ONE HALIDE SALT FROM THE GROUP CONSISTING OF ALKALI METALHALIDES AND ALKALINE EARTH METAL HALIDES AND WHICH IS STABLE ATTEMPETATURES ABOVE 350*C.; CHARGING PARTICLES OF FINELY DIVIDED TITANIUMCARBIDE INTO SAID MELT WHILE IT IS MAINTAINED MOLTEN AT A TEMPERATUREBELOW ABOUT 600*C.; AND INTRODUCING A HALIDE FROM THE GROUP CONSISTINGOF HF AND HCI INTO SAID CARBIDE-CONTAINING MELT WHEREIN IT REACTS WITHTHE CARBIDE TO FORM THE CORRESPONDING TITANIUM TRIHALIDE IN SAID MELT.